In many areas of technology it is necessary to perform load tests on components before they are installed or used. Devices are known for applying loads/forces to or against components. The devices also include structures that counteract or resist the applied forces, that is, structures that hold at least a portion of the tested component in place while the forces are applied. The nature and magnitude of the applied force or forces depend on the size of the components and the forces that they are expected to encounter when in use.
Such load tests are sometimes performed in the field of wind energy. Components to be tested may include, for example, gondolas of wind turbines, bearing assemblies, and/or individual large bearings. However, due to the size and nature of the components to be tested, relatively large forces need to be applied. The structures that resist these forces, that is, that hold the object to be tested in place against the application of a test force, likewise may need to be very large. This takes up unnecessary space and may affect the stability of the test device or a foundation of the test device. Conventional devices may lack adequate stiffness to handle the test forces. Furthermore, it may be difficult to access or view a test object because of an arrangement of the testing device, and this can complicate a load test. Furthermore, the dimensioning requirements and stability requirements for accommodating large loads can lead to additional costs. These or similar problems can also arise when load testing components intended for use outside the wind energy field.
FIG. 1 shows a conventional device 100 for load testing a large bearing 110. The device 100 includes a load-generating unit 130 and a load-reaction unit 140 attached to a foundation 120. The load-generating unit 130 comprises a shaft 150 that is coupled on one end to a motor 160 and that carries the large bearing 110 on an opposite end. The load-reaction unit 140 contacts or connects to the large bearing 110.
The load-generating unit 130 is configured to exert an axially or radially acting force or a moment, e.g., torque, on the shaft 150, which force is transmitted to the bearing 110. In addition, the motor 160 can rotate the bearing 110. The load-reaction unit 140 resists or acts against the force. In other words the load-reaction unit 140 resists the force so that the force acts at least partially on the bearing 110 instead of, e.g., pushing the bearing away from the load-generating unit 130. The force is transmitted via a force-transmission path 170 shown in the form of a closed loop. In other words, the force is applied against or received at least partially by the shaft 150, the bearing 110, the load-reaction unit 140, the foundation, and the load-generating unit 130.
A portion of the generated force that acts on the bearing 110 can be at least 4 MN, and a torque applied on the bearing 110 can be at least 10 MNm. This may correspond to loads that may be encountered by the bearing 110 when used in a wind turbine. It can be difficult for a load-reaction unit 140 to resist such large forces, and accommodating such forces can place unnecessarily high requirements on a stability of the device 100 or its components, e.g., the load reaction unit 140, the foundation 120, or the load-generating unit 130. Furthermore, under certain circumstances this device 100 can have an inadequate stiffness (inadequate to resist applied forces), occupy an unnecessarily large amount of space (because the load-reaction unit must be made very large to accommodate expected forces), or entail high manufacturing costs. In addition, the bearing 110 may be difficult to access or see, and thus difficult to monitor during a test.